Abstract. The present work analyses the effect of dust aerosols on the surface and top
of atmosphere radiative budget, surface temperature, sensible heat fluxes,
atmospheric heating rate and convective activity over West Africa. The study
is focused on the regional impact of a major dust event over the period of
7–14 March 2006 through numerical simulations performed with the mesoscale,
nonhydrostatic atmospheric model MesoNH. Due to its importance on radiative
budgets, a specific attention has been paid to the representation of dust
single scattering albedo (SSA) in MesoNH by using inversions of the AErosol
RObotic NETwork (AERONET). The radiative impacts are estimated using two
parallel simulations, one including radiative effects of dust and the other
without them. The simulations of dust aerosol impacts on the radiative
budget indicate remarkable instantaneous (at midday) decrease of surface
shortwave (SW) radiations over land, with regional (9°–17° N,
10° W–20° E) mean of −137 W/m2 during the 9 to 12 March period. The
surface dimming resulting from the presence of dust is shown to cause
important reduction of both surface temperature (up to 4°C) and sensible
heat fluxes (up to 100 W/m2), which is consistent with experimental
observations. At the top of the atmosphere, the SW cooling (regional mean of
−12.0 W/m2) induced by mineral dust is shown to dominate the total net
(shortwave + longwave) effect. The maximum SW heating occurs within the
dusty layer with values comprised between 4 and 7° K by day and LW
effect results in a cooling of −0.10/−0.20° K by day. Finally, the
simulations suggest the decrease of the convective available potential
energy (CAPE) over the region in the presence of mineral dust.